The Signal Processing Of Transmitter In High-speed Real Time Optical OFDM System Based On FPGA

As with high spectral efficiency and high anti-multipath capabilities of OFDM technology matures in the field of wired and wireless communications, as well as the dispersion of high speed data transmission in optical fiber communication distance problem is becoming increasingly serious, OFDM technology is applied to the optical fiber transmission system to improve the performance of optical transmission signal. Optical orthogonal frequency division multiplexing (O-OFDM) is a new type of optical transmission technology, which combines the advantages of digital signal processing (DSP) and fiber-optic communications technology, not only can resist the chromatic dispersion in optical fiber transmission link, polarization mode dispersion (PMD) and nonlinear effects of factors can also increase the spectral efficiency of the system, thereby greatly enhancing its transmission capacity.O-OFDM technology has become one of the most potential of next-generation high-speed optical communication systems technology, received extensive attention and research.However traditional O-OFDM digital signal processing in optical fiber transmission systems are mostly offline, as the O-OFDM processing speed increases and business applications, the offline approach can not meet the requirements of commercial and real-time processing. Therefore, the real-time processing system of high-speed O-OFDM is particularly important. Recently, foreign real-time implementations of optical OFDM transmitters, receivers and transceivers have been demonstrated using field programmable gate arrays (FPGA).FPGA architecture and logic unit flexibility, high integration, low prices and wide scope of the advantages of large-scale circuit,the programming is more flexible; It also has a strong real-time and parallel processing capabilities, can reduce signal processing latency, scalability and other advantages while its real-time signal processing is made possible. Therefore, further exploratory work is based on the O-OFDM transmission systems FPGA-based, the research can be divided into the following sections:Firstly, this paper take based on the FPGA O-OFDM real time system baseband signal processing as the object of study, analysis of the direct detection of OFDM Systems (DDO-OFDM) and OFDM coherent detection system (CO-OFDM) design of the structure, principle and Foundation programmers. Deep research based on FPGA O-OFDM system’s key technologies and difficulty. Secondly, it combined with XILINX ISE software development platform for OFDM baseband system modeling and it’s based on the design of the I-Q modulation high speed O-OFDM real-time system with signal processing to achieve a1Gbit/s rate of the OFDM signal transmission.Thirdly, overall system performance of OFDM transmitters baseband functional testing and simulation, the key technology for OFDM signal IFFT/FFT in different number of quantization bits error vector magnitude (EVM) carried out a study, and raised an IFFT/FFT algorithm with improved operational precision. The experimental results gave the error vector magnitude (EVM) of IFFT/FFT with different quantification bits. And the EVM value of OFDM signal through IFFT-FFT is declining with the quantization of the increase in the number of bits and the related constellation get a better convergence.